title: Consistency of the efficacy of cetirizine and ebastine on skin reactivity.
abstract: BACKGROUND
  At therapeutic dosage, cetirizine and ebastine induce significant inhibition of skin reactivity to histamine. The consistency of their efficacy, that is, efficacy with the least interindividual variability among subjects, has not been carefully assessed, however.
  
  
  OBJECTIVE
  To compare the consistency and efficacy of these antihistamines on skin reactivity.
  
  
  METHODS
  Twenty-four healthy volunteers participated in a randomized double-blind crossover study. The areas of wheals and flares induced by increasing (0, 5, 10, 50, 100, 200, and 300 mg/mL) histamine concentrations, administered by prick tests, were measured before and four hours after intake of 10 mg of each antihistamine, allowing concentration-response curves to be established. The threshold histamine concentrations inducing wheal areas of 3 mm2 (positivity) were calculated by interpolation. The coefficient of variation (SD/mean %) was used to evaluate the consistency of the response.
  
  
  RESULTS
  Pretreatment concentration-response curves were similar, and threshold concentrations identical (0.29 mg/mL and 0.34 mg/mL for cetirizine and ebastine, respectively). For both, curves were lower after treatment than before. After cetirizine, the threshold concentration was significantly higher (217 mg/mL) than after ebastine (0.82 mg/mL) (P < .001), and total inhibition of the wheal reaction was observed in 21 of 24 patients at the lowest histamine concentration and in 17 of 24 at the highest. Ebastine never totally inhibited reaction, even to 5 mg/mL of histamine. Over the entire concentration-response curve, the coefficient of variation for the wheal reaction was 6.3% for cetirizine and 72.6% for ebastine, and, for flares, 11.0% and 83.7%, respectively. Hence, variability was much lower after cetirizine.
  
  
  CONCLUSIONS
  Our study shows clearly that the efficacy of a single therapeutic dosage of cetirizine is consistently good for suppression of cutaneous reactivity to histamine in healthy volunteers. The need for ebastine to metabolize into the active carebastine might explain its lesser consistency.
authors.affiliation: INSERM U 425, Service de Pneumologie, Hôpitaux Universitaires, Strasbourg, France.
authors.forename: N
authors.initials: N
authors.lastname: Frossard
authors.forename: M
authors.initials: M
authors.lastname: Melac
authors.forename: O
authors.initials: O
authors.lastname: Benabdesselam
authors.forename: G
authors.initials: G
authors.lastname: Pauli
mesh_terms: D000328:Adult; D000707:Anaphylaxis / Q000139:chemically induced / Q000188:drug therapy*; D002090:Butyrophenones / Q000009:adverse effects / Q000627:therapeutic use*; D017332:Cetirizine / Q000009:adverse effects / Q000627:therapeutic use*; D018592:Cross-Over Studies; D017449:Dermatitis, Allergic Contact / Q000209:etiology / Q000517:prevention & control*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006632:Histamine / Q000009:adverse effects; D006634:Histamine H1 Antagonists / Q000009:adverse effects / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D010880:Piperidines / Q000009:adverse effects / Q000627:therapeutic use*; D012449:Safety; D012867:Skin / Q000187:drug effects*; D012882:Skin Tests
chemical_list: D002090:Butyrophenones; D006634:Histamine H1 Antagonists; D010880:Piperidines; D006632:Histamine; C058249:ebastine; D017332:Cetirizine